1. Field of the Invention
The present invention generally relates to systems for sensing electrical currents in integrated circuits that are assembled from standard cells.
2. State of the Art
In the design of modern mixed signal integrated circuits, including application-specific integrated circuits, complex analog functions often can be implemented by assembling appropriate "standard cells" such as operational amplifiers. Because standard cells provide well-defined internal and external characteristics, they can be used for rapidly designing and fabricating integrated circuits.
When designing integrated circuits that include standard cells, it is often desirable to determine the values of current and voltage parameters that are internal to the cells. Although such measurements can be made by circuits that are designed into a standard cell, the mere presence of designed-in sensing components renders a standard cell "non-standard." Also, designed-in sensing components can adversely affect the output characteristics of a standard cell, especially when the cell is used in low voltage applications.